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I I
R e p o r t N o I I T R I - I J 6 0 1 8 - 1 ( F i n a l R e p o r t )
PREPARATION O F S-13 EXPERIMENTAL COATINGS
N a t i o n a l A e r o n a u t i c s
G e o r g e C. Marshall Space F l igh t C e n t e r and Space A d m i n i s t r a t i o n -
- - . ,.a
I I I R E S E A R C H \ I N S 1 I T U T E
\
I ' 1. I
R e p o r t N o , I I T R I - U 6 0 1 8 - 1 ( F i n a l R e p o r t )
PREPARATION O F S-13 EXPERIMENTAL COATINGS
O c t o b e r 24, 1963, through A u g u s t 31, 1965
C o n t r a c t N o , NAS8-11967 I I T R I P ro jec t U 6 0 1 8
Prepared by
G o A, Z e r l a u t
of
I I T RESEARCH I N S T I T U T E T e c h n o l o g y C e n t e r
C h i c a g o , I l l i n o i s 60616
for
N a t i o n a l A e r o n a u t i c s and Space A d m i n i s t r a t i o n G e o r g e C. Marshall S p a c e F l i g h t C e n t e r
H u n t s v i l l e , A l a b a m a
COPY N o , 13 December 1 4 , 1965
I l l R E S E A R C H I N S T I T U T E
.
FOREWORD
This i s Report N o , IITRI-U6018-1 (F ina l R e p o r t ) of I I T R I
P ro jec t U6018, e n t i t l e d "Preparation of S-13 Experimental C o a t -
ings , '# The work descr ibed i n t h i s r e p o r t was sponsored under
t w o cont rac ts : C o n t r a c t No, NAS8-11133 ( I I T R I Project C6025,
October 29, 1963, t o March 15 , 1965) and Contract No. NAS8-
11967 ( I I T R I P ro jec t U6018, Apri l 20 t o August 31, 1965).
Thus the report covers t he period from October 29, 1963, through
August 31, 1965. The work was administered under the t echn ica l
Mater ia l s Division of t h e George C. Marshall Space F l i g h t Center,
with M r . L o w e l l K. Zoller a c t i n g a s P ro jec t Engineer.
Major con t r ibu to r s t o the program include Gene A. Zer lau t ,
Project Leader; Warren Jamison and Douglas Vance, space-
s imulat ion tests: and Douglas Vance and Noel Bennett , p a i n t and
specimen prepara t ion and op t i ca l -p rope r t i e s measurements,
Data a r e recorded i n I I T R I Logbook C14462,
Respectfully submi t t ed , I I T RESEARCH INSTITUTE
Approved by: Gene A. h f d a u t Research Chemist-Group Leader Polymer R e search
T, H. Meltzer Manager Polymer R e search
GAZ: j a b
I l l R E S E A R C H I N S T I T U T E
IITRI-U6018-1 ii
/
TABLE OF CONTENTS
I ,
I1 0
I11 0
I V .
V.
V I 0
V I 1 0
V I 1 1 0
Introduct ion
History of S-13 Thermal-Control Paint
Composition
Delivery Schedule
Pa in t Preparat ion
A. I n i t i a l Manufacturing Procedure
B. F ina l Manufacturing Proc+edure
C ., Qual i ty-Control Data
Inves t iga t ion of Mill-Yellowing and Pa in t I n s t a b i l i t y
Cognate S tudies by Other Organizations
Conclusions
Appendix I - S-13 P a i n t Spec i f ica t ion , Modification I1
Appendix I1 - Measurement of Thermophysical P rope r t i e s
Appendix I11 - Space (Solar ) Simulation Chambers
References
Page
1
2
3
4-
5
5
9
9
I I T R E S E A R C H I N S T I T U T E
I I T R I - U 6 0 18- 1 iii
15
18
20
21
26
28
LIST O F TABLES AND FIGURES
TABLE
1 S-13 Delivery Schedule
2 E f fec t s of U l t r a v i o l e t I r r a d i a t i o n i n Vacuum on Specimens of S-13 Pegasus P a i n t ( F i r s t D e l i very)
3 E f fec t s of U l t r a v i o l e t I r r a d i a t i o n i n Vacuum on Specimens of S-13 Pegasus Pa in t (Second D e l i very)
5 Effec t of U l t r a v i o l e t I r r a d i a t i o n i n Vacuum on Specimens of S-13 Pegasus P a i n t Prepared a t Cape Kennedy f o r SA-9 (Pegasus I)
6 Tota l Normal Emittance of S-13 Specimens (Delivery 1, C o m p o s i t e s )
7 To ta l Hemispherical Emittance of S-13 Specimens (Delivery 4 , Composites)
FIGURE
1 Ef fec t of Duration of Grinding on S t a b i l i t y of S-13 Pa in t
2 VacLon Solar Simulation Chamber
3 Quad-Ion Solar Simulation Chamber
Page
5
e E
I I T R E S E A R C H I N S T I T U T E
1 V IITRI-U6018-1
7
8
10
13
:: 4
15
17.
29
30
L
PREPARATION O F S-13 EXPERIMENTAL COATINGS
I e INTRODUCTION
The hea t - t r ans fe r ana lys i s ( r e f , 1) of t h e three Pegasus
spacec ra f t launched during 1965 showed t h a t po r t ions of t h e
spacec ra f t , t h e S - I V s t age , the instrument u n i t ( I U ) , and the
A p l l o service-mdule adaptor ( S N A ) of t h e Saturn I iauncn
vehic le required a coat ing w i t h a solar absorptance, a, of u,i8
t o 0.36 and an i n f r a r e d emittance, E ~ , of about 0.9 throuqhout
the s p a c e c r a f t ' s 1-yr o r b i t a l l ifetime., L .
A z inc oxide-pigmented polydimethylsiloxane coa t ing was
chosen a f t e r c a r e f u l considerat ion of t h e f a c t o r s involved.
Factors considered w e r e u l t r a v i o l e t s t a b i l i t y , commercial ava i l -
a b i l i t y of cons t i t uen t s , ease of app l i ca t ion of and maintenance
of p r o p e r t i e s , and low-temperature c h a r a c t e r i s t i c s , Low-
temperature c h a r a c t e r i s t i c s are of some importance s ince the
S - I V s t a g e i s fue led wi th l i q u i d hydrogen, The p a i n t chosen was
designated S-13 and w a s developed by I I T Research I n s t i t u t e
under t h e i n i t i a l sponsorship of t he J e t Propulsion Laboratory
of t h e Ca l i fo rn ia I n s t i t u t e of Technology ( re f . 2,3). Addi-
t i o n a l S-13 development e f f o r t s were performed under t h e sponsor-
s h i p of the Marshall Space F l i g h t Center (ref * 4,5) - S-13 was chosen because of i t s except iona l ly high s t a b i l i t y
to u l t r a v i o l e t i r r a d i a t i o n i n vacuum, a c h a r a c t e r i s t i c t h a t i t
exh ib i t ed i n numerous tests, The comparatively l a r g e amount of
ground-testing da ta t h a t had been accumulated on S-13, e s p e c i a l l y 111 R E S E A R C H I N S T I T U T E
1 IITRI-U6018-1
solar-s imulat ion-effects information, weighed heavi ly i n i t s
choice f o r use on t h i s mission,
q u a n t i t i e s t o the production q u a n t i t i e s requi red for the three
Pegasus spacecraf t represented an important advancement i n the
s t a t e of the a r t of spacecraf t temperature-control coat ings f o r
f i e l d use, I t was recognized ea r ly t h a t the l a r g e S - I V s tage
would have t o be pa in ted on loca t ion a t Cape Kennedy and t h a t
the painted vehic le would probably stand on the launch pad f o r
a considerable t i m e prior t o launch,
The scale-up from labora tory
A s a consequznze of this program, a g r e a t dea l has been
learned about the appl ica t ion of thermal-control coa t ings t o
l a r g e space vehic les and about the maintenance of such coat ings
during prelaunch and launch operat ions,
11, HISTORY O F S-13 THERMAL-CONTROL PAINT
Two zinc oxide-pigmented thermal-control coa t ings developed
f o r t h e J e t Propulsion Laboratory ( re f , 2,3) under Contract No,
950111 (subcontract under NASA Contract No, NAS7-100) were
found to have f i e ld -app l i ca t ion p o t e n t i a l , One i s I ITRI ' s 2-93
coa t ing , w h i c h u t i l i z e s potassium s i l i c a t e as t h e vehic le , and
the o t h e r i s the S-13 coat ing, which i s based upon a commercial
elastomeric methyl s i l i c o n e polymer,
The inorganic 2-93 coat ing, w h i l e possessing l o w e r s o l a r
absorptance than S-13, has a very s h o r t she l f - l i f e , S-13, on
the o t h e r hand, has exce l l en t s h e l f - l i f e and i s r e l a t i v e l y easy
l l T A E S E A R C H I N S T I T U T E
2 IITRI-U6018-1
t o apply and maintain. As a consequence, it has received con-
s ide rab le a t t e n t i o n a s a candidate white thermal-control
coat ing.
For these reasons a s wel l as those discussed e a r l i e r , S-13
was chosen a s the white thermal-control p a i n t f o r Pegasus space-
c r a f t and the assoc ia ted Saturn upper s tages , T h i s app l i ca t ion
requi red the manufacture of over 1 4 5 ga l of S-13 pa in t .
I n addi t ion t o being used on Pegasus I , 11, and 111, S-13
was used a s the so l e thermal-control coat ing on the Explorer-24
I n j u n s a t e l l i t e ( t i n t e d green t o achieve a s o l a r absorptance of
0.55) and on the A i r Density Explorers X I X and XXIV ( r e f . 6) . S-13 c u r r e n t l y i s being considered f o r use on a number of space-
c r a f t
111, COMPOSITION
S-13 i s a z inc oxide-pigmented polydimethylsiloxane i n
to luene , The zinc oxide i s SP500 obtained from the New Jersey
Zinc Company, he methyl s i l i c o n e vehirle is RTV-602j a linear
polymer obtained from the General E l e c t r i c Company. The curing
agent i s General E l e c t r i c ' s p ropr ie ta ry SRC-05 c a t a l y s t , I t
i s added j u s t p r i o r t o appl ica t ion of t he p a i n t and i s 0.4 t o
1.0% by weight of RTV-602 i n the p a i n t . The lower c a t a l y s t
concent ra t ion i s prefer red from the s tandpoin t of u l t r a v i o l e t
s t a b i l i t y , bu t a concent ra t ion of 0.76% was used f o r the Pegasus
p a i n t as a s a t i s f a c t o r y compromise between optimum physical
p r o p e r t i e s and maximum s t a b i l i t y of o p t i c a l p rope r t i e s .
l l T R E S E A R C H I N S I I T U T E
3 IITRI-U6018-1
I . The composition of S-13 pa in t furnished f o r app l i ca t ion t o
I
t he Pegasus spacecraf t was:
Const i tuents Par ts by Weiqht
New Jersey Zinc SP500 z inc oxide 240 General Electr ic RTV-602 s i l i c o n e 100 Toluene 170
The SRC-05 c a t a l y s t was added a t 1 p a r t per 670 p a r t s by weight
of t h e S-13 p a i n t furnished. The c a t a l y s t was added a s a 3%
s o l u t i o n i n toluene; t he p a i n t was furnished wi th a so lvent
holdout of approximately 15 p a r t s by weight based on the formula
c i t e d
The p a i n t can be appl ied t o any sur face t o which t h e p r i m e r
w i l l adhere, The primer, which i s General E l e c t r i c ' s SS-4044,
must be used t o prevent s t r i p p i n g of t h e cured S-13. The
p r i m e r i s appl ied a t a thickness of about c.5 m i l (0.0005 i n . )
and r e q u i r e s 1 h r of drying time prior t o app l i ca t ion of t h e
S-13. It usua l ly i s recommended t h a t both the primer and the
S-13 be spray-applied t o o b t a i n best r e s u l t s , More d e t a i l e d
instructians are cantained i:: the s-13 specif icat ian, Appen-
d i x I.
I V , DELIVERY SCHEDULE
One hundred and foi r t y - f i 1 ga l lons of p a i n t w e r e furnished
t o t h e George C. Marshall Space F l i g h t C e n t e r under the t e r m s
of t h e two app l i cab le con t r ac t s , The de l ive ry schedule i s
presented i n Table 1. Del iver ies 4 through 11 w e r e made t o
t h e Kennedy Space F l i g h t C e n t e r , Cape Kennedy, F lor ida ,
111 R E S E A R C H I N S r l T U T E
4 IITRI-U6018-1
Table 1
S-13 DELIVERY SCHEDULE
I
No,
1 2 3 4 5 6 7 8 9
i o 11
Delivery D a t e
D e c e m b e r 9, 1963 January 8, 1964 A p r i l 8, 1964 (pas te ) Apr i l 29, 1964 May 13, 1964 Ju ly 13, 1964 (pas te ) March 2: 1965 March 8, 1965 May 3, 1965
June 7, 1965 Msy 7 , 1965
Quant i ty
10 g a l 30 g a l 5 l b 25 g a l 15 g a l 20 l b 5 g a l
10 gal 10 gal
5 g a l 3r; - 3 1 &J y u r
Applicable Contract
NAS8-11133 NAS8-11133 NAS8-11133 NAS8-11133 NAS8-11133 NAS8-11133 NAS 8- 119 6 7 NAS8- 119 6 7 NAS8-11967 ?!:..\s 8- 1 19 6 -7 NAS8-119 67
The de l ive ry of 5 g a l of pa in t on June 7, 1965, was made
a f t e r it was learned t h a t one 5-gal p a i l , de l ivered on May 3,
1965, w a s de fec t ive when opened a t t he Kennedy Space F l i g h t
C e n t e r
V. PAINT PREPARATION
A, I n i t i a l Manufacturinq Procedure
The f i r s t 40 g a l of S-13 pain t w e r e pebble-milled i n
5-gal ba tches using t w o 6-gal capaci ty borundum-fortified
p - c e l a i n j a r s . The m i l l s w e r e one-half f u l l of c y l i n d r i c a l
po rce l a in s tones 3/4 i n . i n diameter and 3/4 i n , long. The
m i l l s w e r e charged wi th a pigment-vehicle-solvent s l u r r y pre-
pared according t o t h e formula spec i f i ed i n Sect ion I11 except
t h a t 70 p a r t s by weight of t h e toluene w e r e he ld out . The
111 R E S E A R C H I N S I I T U T E
IITRI-U6018-1 5
s l u r r y was ground a t approximately 70% of c r i t i c a l speed
(-40 rpm) f o r 8 h r , The m i l l was then discharged and the re-
maining toluene w a s added. T h e solvent-r ich s l u r r y was ground
f o r approximately 5 min, and the conten ts w e r e then added t o
the main charge, T h e p a i n t w a s thoroughly mixed.
T e s t specimens w e r e prepared and subjected t o 2000 equiva-
l e n t sun-hours (ESH) of u l t r a v i o l e t r a d i a t i o n i n vacuum, The
f a c i l i t i e s f o r measurement of o p t i c a l p r o p e r t i e s and f o r u l t r a -
v i o l e t i r r a d i a t i o n i n vacuum a r e descr ibed i n Appendices I1
and III? respec t ive ly , The r e s u l t s of the space s imulat ion
tests on the f i r s t 40 g a l of S-13 a r e presented i n Tables 2
and 3,
The s o l a r absorptance increase , nus, exhib i ted by specimens
prepared from the f i r s t 40 g a l of S-13 was d isappoin t ing ly high.
The i nc reases i n s o l a r absorptance w e r e from 0,05 t o 0-08 a f t e r
exposure t o 2000 ESH of u l t r a v i o l e t r a d i a t i o n i n vacuum. L i t t l e
improvement i n nas w a s noted when the u l t r a v i o l e t i r r a d i a t i o n
.;,.as perfcrxed w i t h the subs t r a t e s maintained a t nominal tem-
p e r a t u r e of -38OF.
An i n v e s t i g a t i o n showed t h a t the i n s t a b i l i t y of t hese
specimens was d i r e c t l y r e l a t e d t o the gr inding t i m e and t o the
shear forces present i n the m i l l . This i nves t iga t ion i s de-
scribed i n Sect ion V I ,
The George C , Marshall Space F l i g h t Center was subsequently
advised t o discont inue use of the f i r s t 40 g a l of S-13 (except
for the purpose of developing scale-up procedures f o r pa in t ing
111 R E S E A R C H l N S 1 l f u f ~
6 I I T R I -U6 018- 1
T a b l e 2
EFFECTS O F ULTRPiVICLET 1,PRADIATION I N 'JAC'u"JM ON SPECIMENS OF S-13 PEGASUS PAINT ( F I R S T DELIVERY)
Solar A b s o r p t a n c e B a t c h E x p o s u r e
Specimen Mill Size , s a l Solar Factor ESHa as A%
1 A 5
.*
1 B 5
0 0 0.181 9,2 1700 0.218 0.037
0 0 0.185 9,2 1700 0.209 0.024
1 A + B 10 0 0 0.172 10.5 2100 0.252 0.080
2 A 5
2 B 5
0 0 0.186 9.2 1700 0.217 0.031
0 0 0.199 9.2 1700 0.225 0.026
2 A + B 10 0 0 0,179 10,5 2100 0.236 0.057
~~
a E q u i v a l e n t sun-hours of u l t r a v i o l e t exposure i n vacuum.
7 I I T R I -U60 18- 1
Table 3
EFFECTS OF ULTRAVIOLET IRRADIATION IN VACUUM ON SPECIMENS OF S-13 PEGASUS PAINT (SECOND DELIVERY)
Solar Sq3L 4- UusLrate Absorptance Temperature, Exposure
C-l-.* P = n C r \ r zsE a, Y L ) u I a L I u L L v I
"F S pe ci me na
1
2
3
4
5b
6
- 7
8
45
45
45
45
-38
-38
-38
-38
0 1 2
0 1 2
0 1 2
0 1 2
0 10,7
0 10,7
0 1 1 , 7
0 11,7
0 2000
0 2000
0 2000
0 2000
0 2000
0 2000
0 2000
0 2000
0 ., 209 0 0 268
0 204 0,274
0,202 0 ., 269
0,197 0 256
0 ., 206 0 273
0 0 199 0,258
0,197 0.254
0 204 0 , 264
4% - --
0,059
0.070
0,067
0 . 059
0,067
0 , 059
0.057
0,060
a 30-gal batch, specimens were prepared from the 30-gal composite.
The six 5-gal batches were mixed and the
bSoiled with pump oil and cleaned with 10% solution of Alconox.
8 I ITRI-U60 18-1
t
the l a r g e Saturn S - I V s t a g e ) . The p a i n t prepara t ion procedures
w e r e modified accordin2ly; t h e following paragraphs describe
the procedure adopted f o r t he manufacture of the remainder of
the Pegasus p a i n t ,
B, F ina l Manufacturinq Procedure
The manufacturing procedure adopted f o r the remaining
105 gal cf S-13 invc1ved (1) replacement of t h e c y l i n d r i c a l
,-'C-n..- - 7 4 CL 3Lu11G3 w I L l l sphe r i ca l grifidifig media 0 ,5 ir?, ir? d i a m e t e r 7
( 2 ) reduct ion of the volume of the gr inding media by 50% ( the
m i l l s w e r e 1 /4 f i l l e d w i t h stones) and ( 3 ) reduct ion of the
gr inding t i m e t o 3 h r ,
T h e use of sphe r i ca l s tones g r e a t l y reduced the i n t e r -
f a c i a l contac t a r e a i n comparison t o the u s e of c y l i n d r i c a l
s tones , Each stone-stone i n t e r f a c e became a p o i n t con tac t i n
c o n t r a s t t o the l i n e contac t prevalent w i t h c y l i n d r i c a l grind- I l i n g media, Reduction of the volume of t h e gr inding media I reduced the weight component of the shear forces required t o
e f f e e t pigment d i spe r s ion , These changes, coupled wi th the
reduct ion of the gr inding t i m e t o 3 h r , r e s u l t e d i n increased
s t a b i l i t y of the S-13 p a i n t and d i d not adversely affect the
i n i t i a l s o l a r r e f l ec t ance c h a r a c t e r i s t i c s of the S-13 f i lms .
I ! I I I
C, Qual i ty-Control Data
-The r e s u l t s of the qua l i ty -cont ro l space-simulation tes t - I
i n g of the remaining p a i n t d e l i v e r i e s a r e presented i n Table 4 .
Each specimen noted i n Table 4 was prepared f rom a composite of
I I
l l i R E S E A R F H I N S T I T U T E
9 IITRI-U6018-1
Table 4
EFFECT OF ULTRAVIOLET IRRADIATION I N VACUUM ON SPECIMENS OF S-13 PMiAsUS PAINT (DELIVERIES 3 THROUGH 11)
So la r Abso r D t ance Catalyst Batch Delivery Exposure
Specimen Conc.! X Size N o . Solar Factor a US - A%
Pas t e 0.76 5 l b 3 0 0 0.184 12.4 2000 0.220 0.036
4-1 0.76 25 g a l 4 0 0 0.174 10 2000 0.221 0.047
5010 0.76 25 g a l 4 0 0 0.196 10 2000 0.217 0.021
E3- 1 0.4 A * 1 K - 2 1 .. U A 5 0 0 0.?.9? 10 2000 0.206 0.009
B-2 0.4 15 g a l 5 0 0 10 2000
B=3 0 . 4 -4 l r ; m = l - j W A - I! c!
E-4 0.4 15 g a l 5 0 0 10 2000
Pas t e 0 . 4 20 lb 6 0 0 10 2000
r;
10 2000
0.203 0.217 0.014
c!. 188 0.205 0.017
0.198 0.209 0.011
0.189 0.205 0.016
5124 0.76 15 g a l 7 & 8 0 0 0.212 10 2000 0.234 0.022
5125 0.76 15 g a l 7 61 8 0 0 0.217 10 2000 0.235 0.018
5150 0.76 10 g a l 9 0 0 0.181 10 2150 0.205 0.024
5151 0.76 10 g a l 9 0 0 0.179 10 2150 0.213 0.034
5152 0 .76 30 ga l 10 & 11 0 0 0.173 10 2150 0.208 0.035
5153 0.76 30 g a l 10 & 11 0 10
0 0.175 2150 0.203 0.028
10 IITRI-U6018-1
t h e e n t i r e de l ive ry , or d e l i v e r i e s , as noted, For example,
specimens 4-1 and 5010 w e r e prepared from a composite of
samples taken from each of the f i v e 5-gal batches tha t con-
s t i t u t e d de l ive ry 4 , On the o ther hand, specimens 5124 and
5125 w e r e prepared f r o m a composite of two d e l i v e r i e s , 7 and 8 ,
which w e r e 5 and 10 g a l , respec t ive ly , Likewise, specimens
5152 and 5153 w e r e made up from a composite prepared f r o m de-
l i v e r i e s 10 and 11,
T h e i nc reases i n s o l a r absorptance, Las, observed f o r the
specimens shown i n Table 4 w e r e of the magnitude expected.
T h e modif icat ions i n the paint-preparation procedure w e r e s u f f i -
c i e n t t o reduce the e f f e c t s of gr ind t i m e and shear fo rces t o
a t o l e r a b l e l e v e l , The lower so l a r absorptance inc reases
observed f o r the specimens prepared from d e l i v e r i e s 5 and 6 a r e
thought t o r e s u l t f r o m the lower c a t a l y s t concentrat ion used t o
prepare these samples, T h i s lower concentrat ion of 0,4% (based
upon RTV-602) was inadve r t en t ly u s e d ‘to prepare these specimens,
Specimens subjected t o u l t r a v l o l e t i r r a d i a t i o n i n vacuum
a f t e r February 1965 w e r e thermally evacuated (150OF a t to r r )
f o r 10 t o 16 hr p r i o r t o u l t r a v i o l e t i r r a d i a t i o n , T h i s proce-
dure ensured thorough curing of a l l S-13 specimens and precluded
t h e p o s s i b i l i t y of photo lys i s of unreacted polymer and c a t a l y s t ,
w h i c h can migrate t o the surface.
T e s t specimens w e r e prepared a t Cape Kennedy by Douglas
A i r c r a f t personnel when the launch vehic les w e r e painted, T h e
aluminum s u b s t r a t e s w e r e loca ted on the SA-9 instrument u n i t
I l T R E S E A R C H I N S T I T U T E
11 I I T R I -U60 18- 1
( I U ) , the S - I V , and the service-module adaptor (SMA) s t ages and
w e r e coated a t t h e t i m e t h e s tages w e r e painted. T h e specimens
w e r e subjected t o the same environment as the v e h i c l e , and t w o
from each s t age w e r e subsequently submitted t o I I T Research
I n s t i t u t e f o r space-simulation t e s t i n g , The SA-9 s t ages ( I U ,
S - I V , and SMA) w e r e cleaned w i t h a 10% Alconox (Alconox Inc , )
so lu t ion and copious q u a n t i t i e s of d i s t i l l e d w a t e r 1 week p r i o r
t o launch, Specimens 5118 through 5123 received the s a m e t reat-
men t , w e r e mounted i n t h e Launch Complex 39 Service Tower, and
w e r e subjected t o the same Cape Kennedy environmental condi t ions
as the e n t i r e SA-9 vehicle , The specimens w e r e removed sub-
sequent t o launch and submitted to I I T R I without f u r t h e r t reat-
ment, The r e s u l t s of exposure of these con t ro l specimens t o
2000 ESH of u l t r a v i o l e t i r r a d i a t i o n i n vacuum are presented i n
Table 5,
F i l m was removed f r o m SA-9's I U s t a g e by the author a f t e r
it w a s cured on November 4 , 1964, the day the s t age was painted,
This d e k z ~ h ~ d f i l m is l a b e l e d "free f i l m " in Table 5, I t T.r-p m u =
subjected t o 450 ESH immediately af ter SA-9 w a s launched i n
o rde r t o a s c e r t a i n whether a n anomaly noted i n the prel iminary
temperature da t a w a s due to defec t ive S-13. The very l o w s o l a r
absorptance increase, Ass, of 0,005 as w e l l as the r e s u l t s of
the exposure tests on t h e control samples submitted t o I I T R I
by NASA i n d i c a t e t h a t the S-13, a s appl ied , w a s a s s t a b l e a s
p red ic t ed ,
I l l R E S E A R C H I N S T I T U T E
12 I I T R I - U6 0 18- 1
Table 5
EFFECT OF ULTRAVIOLET IRRADIATION IN VACUUM
PREPARED AT CAPE KENNEDY FOR SA-9 (PEGASUS ij ON SPECIMENS OF S-13 PEGASUS PAINT
Solar Absorptance
A N as --S Thickness,
mils Expo sure
Solar Factor ESH Saturn Staqe Specimen
5118 7 0 0 10 2000
0,195 0.217 0,022
IU
5119 7 0 0 10 2000
0 , 205 0,224 0.019
IU
5120 s-IV 6 0 0 10 2000
0,195 0.216 0,021
0,193 0,218 0.025
5121 s-IV 6 0 0 10 2000
5122 0 0 10 2000
0.229 0.248 0.019
SMA 6
5123 6 0 0 10 2000
0 226 0,245 0.019
SMA
Free f i l m 8 0 0 10 450
0,195 0,200 0.005
IU
13 IITRI-U6018-1
The t o t a l emi t tances of specimens of the S-13 pa in t fur -
nished f o r the Pegasus program are presented i n Tables 6 and 7 ,
The t o t a l normal emittance values (Table 6) were obtained on
the f i r s t de l ive ry of p a i n t , Emittance da t a were not obtained
on the second de l ive ry of p a i n t because of the high AasS ob-
served a f t e r exposure t o u l t r a v i o l e t r ad ia t ion i n vacuum.
Table 6
TOTAL NORMAL EMITTANCE O F S-13 SPECIMENS (DELIVERY 1, COMPOSITES)
Thickness, Total Normal Emittance m i l s ( 30O0F)
5,O 0 -90
5.0 0.82
7 . 3 0.84
907 0.90
Hemispherical emittance data were obtained on c o m _ p o s i t e
specimens prepared from de l ivery 4 ; the t o t a l hemispherical
emit tance values a r e more r e l i a b l e than the t o t a l normal values .
The l e s s r e l i a b l e t o t a l normal values a r e a r e s u l t of low
s igna l - to-noise r a t i o s when the measurements were performed a t
temperatures below 500°F i n t he equipment ava i l ab le a t I I T R I ,
The d a t a a r e contained i n Table 7.
IIT R E S E A R C H I N S T I T U T E
1 4 IITRI-U6018-1
I
I
I
I
I
I I
I
I I
i I
I I
I
I
Table 7
TOTAL HEMISPHERICAL EMITTANCE O F S-13 SPECIMENS (DELIVERY 4 , COMPOSITES)
Thickness, Subs t ra te m i l s Temperature, OF
5
5
6
35 -40
35 -40
35 -40
Total Hemispherical Emittance
0-84 0.86
0,85 0.87
0,86 0,88
Additional t o t a l hemispherical emi t t ance determinat ions
of S-13 specimens w e r e not performed on samples of subsequent
d e l i v e r i e s because (1) funds were d ive r t ed t o underwrite, i n
par t , the s t u d i e s t h a t w e r e required t o solve the mill-yellowing
and i n i t i a l i n s t a b i l i t y problem and (2) these coa t ings had pre-
v ious ly been shown ( r e f , 2,3) t o possess emittances of 0,85
t o 0,90 f o r 5- t o 7 - m i l f i lms.
V I . INVESTIGATION O F MILL-YELLOWING AND P A I N T INSTABILITY
Two problems w e r e encountered i n sca l ing up the prepara-
t i m of the S-13 from small laboratory batches t o 5-gal produc-
t i o n batches. One w a s severe mill-yellowing, which occurred
dur ing t h e gr inding opera t ion ca r r i ed o u t i n the l a r g e porcelain
ba l l m i l l : the o t h e r problem was decreased s t a b i l i t y t o u l t r a -
v i o l e t r a d i a t i o n i n vacuum a s a r e s u l t of gr inding i n the l a r g e
m i l l ,
I l l R E S E A R C H I N S T I T U T E
IITRI-U6018-1 15
Yellowing of z inc oxide powders r e s u l t s from mechanical
d i s t o r t i o n , Mechanical d i s t o r t i o n of z inc oxide can be produced
by scra tch ing t h e sur face of a zinc ox ide - s i l i ca t e coa t ing ,
gr inding the p o w d e r with an agate mortar and pest le , o r compact-
ing the p o w d e r a t high pressures , The very process of p a i n t
manufacture t h a t involves grinding t h e pigment i n t o a vehic le
i n order t o w e t t he p a r t i c l e s causes yellowing when shear fo rces
a r e excessive, Excessive shear forces r e s u l t from too high a
r a t i o of gr inding medium to m i l l charge o r from operat ion of t h e
m i l l a t too high a speed,
Several p a i n t s w e r e prepared by gr inding f o r d i f f e r e n t
lengths of t i m e , Solar absorptance and s t a b i l i t y of s o l a r ab-
sorptance t o u l t r a v i o l e t r ad ia t ion i n vacuum were determined as
a func t ion of g r ind t i m e , Figure 1 shows t h a t s t a b i l i t y i s a
func t ion of t he du ra t ion of grinding: regard less of whether a
small-capacity o r a 5-gal m i l l w a s used, Maximum s t a b i l i t y i s
achieved a f t e r s h o r t grinding t i m e s of only 3 h r , which was t h e
gr indinq t i m e used to prepare the bulk of t h e Pegasus p a i n t ,
The shape of t h e nus curves i n Figure 1 i s explained as
fol lows, The i n t i a l increase i n s t a b i l i t y ( i o e o 7 decrease i n
e f f e c t on s o l a r absorptance) i s a t t r i b u t e d t o an increased
degree of d ispers ion of the pigment, That i s , the i n i t i a l high
i n s t a b i l i t y i s thought t o be due t o photo lys i s of i s l a n d s of
polymer t h a t a r e not pro tec ted by the screening e f f e c t s of t h e
z inc oxide, The mnimum degradation occurs when the b e n e f i t s
I l T R E S E A R C H I N S T I T U T E
16 IITRI-U60 18- 1
--.a, .m a, k U c H
0.1 0
0.09
0.08
0.0 7
0.06
0.0:
0.04
0.03
0.02
0.01
C 0
1 [ I I . I I 5 IO 15 2 0 25
D u r a t i o n of G r i n d , h r
30
0.25
0.2 4
0.2 3
0.22
0.2 I
0.20
0. I 9
0. I 8
0. I 7
0. I 6
0.1 5 35
Figure 1
EFFECT O F DURATION O F GRINDING ON S T A B I L I T Y O F S-13 PAINT
17 I I T R I - U 6 0 1 8 - 1
of improved d ispers ion no longer counterbalance the degrading
inf luence of grinding.
Degradation w a s f i r s t thought t o be due t o s i l i ca contamina-
t i o n a s a r e s u l t of shear ing forces , the e f f e c t s of w h i c h become
important a f t e r long grinding. However, shear ing forces create
l a t t i c e d i s t o r t i o n i n z inc oxide, r e s u l t i n g i n the c r e a t i o n of
an absorpt ion band centered a t 3850 A , which may be respons ib le
f o r t h e observed inc rease i n degradation. T h e p o s s i b i l i t y of
s i l i c a contamination has been ruled o u t by c a r e f u l l y gr inding
ziiic oxide i n ail agate i ~ ~ r t a r and pestle ar?d blending it i n t o
t h e s i l i c o n e elastomer used i n t h e S-13 formulation. Th i swork
w a s performed f o r t h e George C. Marshall Space F l i g h t Center on
another program ( r e f , 4 ) . I n a 1500-ESH t e s t the Aas was 0.049
f o r t h e p a i n t made from stressed z inc oxide. This f i g u r e compared
unfavorably w i t h t h a t of our standard S-13, w h i c h degraded by
0,025 i n the same t e s t ,
0
V I I , COGNATE STUDIES BY OTHER ORGANIZATIONS
A number of s t u d i e s on S-13 have been performed by other
organiza t ions , and t h e i r conclusions have been abs t r ac t ed here
as p e r t i n e n t to t h i s discussion. Zol le r ( r e f . 7) has tabula ted
a v a i l a b l e d a t a on specimens of the S-13 p a i n t appl ied t o t h e
SA-g/Pegasus I spacecraft. H i s da t a included t h e r e s u l t s of
' s tudies performed by t h e Mater ia ls Divis ion of t h e George C.
Marshall Space F l i g h t Center on con t ro l specimens prepared a t
t h e Cape Kennedy launch s i t e , The r e s u l t s of t hese s t u d i e s
e s s e n t i a l l y cor robora te t h e previous da t a on S-13 f i l m s . I l l R E S E A R C H I N S T I T U T E
18 I ITRI - U60 18- 1
Badin ( r e f . & ) reported the r e s u l t s of r a d i a t i v e property
measurements performed a t t h e Kennedy Space Center on the
SA-g/Pegasus I vehicle . T h e Lion Research model 25-A emisso- 0
m e t e r w a s employed f o r i n s i t u t o t a l normal emittance determina-
t i o n s ; the Gier-Dunkle mobile s o l a r re f lec tometer w a s employed
f o r i n s i t u s o l a r absorptance measurements,, Badin concluded
t h a t the effects of contamination, such as f i n g e r p r i n t s and
d u s t c o l l e c t i o n , on the i n i t i a l o p t i c a l and radiometric char-
acter is t ics of the s-13 pain ted sur faces w e r e negl ig ib le . H e
noted t h a t washing the p a i n t w i t n de te rgent [Aiconoxj and water
p r i o r t o launch removed lithe major por t ion of t h i s contamina-
t i o n , " I n two other m e m o s ( r e f . 9 , 1 0 ) , Badin presented the
r e s u l t s of i n s i t u o p t i c a l and radiometric measurements on the
SA-8/Pegasus I1 and SA-lO/Pegasus I11 spacec ra f t , respec t ive ly .
TaT------ 1 m - C C \ L-- -n-n-L l - - A4 n m q * n m n A Lk- .-e-.. 1 4 - m -C L 4 c. l l u ~ . & . , l r ~ \ L T A * v , 11U" L b b b A A C I J - . . h Y " U Y W " U b..." & - " u I c w "I I.+"
s t u d i e s on S-13 (prepared byNASA:s Langley Research Center from
I I T R I s p e c i f i c a t i o n s ) f o r use on the Explorer X I X and
Explorer XXIV A i r Density ( i n f l a t a b l e ) spacecraf t . The d is ten-
s i b i l i t y and maintenance of p rope r t i e s a t l o w temperature made
t h e S-13 p a i n t an a t t r a c t i v e candidate f o r app l i ca t ion to
expandable s t r u c t u r e s . Woerner concluded t h a t t he s o l a r absorp-
tance of S-13 (as w e l l as t h a t of another less stable candidate)
w a s a f f e c t e d much less by e l ec t ron r a d i a t i o n than by u l t r a v i o l e t
r a d i a t i o n f o r equivalent exposure times i n terms of a given
orb i ta l lifetime. H i s da t a a l s o corroborate t h e previously re-
ported d a t a a s w e l l a s t h e information contained i n t h i s communi-
ca t ion . I I T R E S E A R C H I N S T I T U T E
19 IITRI-U6018-1
V I 1 1 CONCLUSIONS
The work described here in has confirmed the e x c e l l e n t
s t a b i l i t y of the S-13 p a i n t formulation t o a simulated space
environment, I t has shown t h a t the p a i n t appl ied t o the Pegasus
I , 11, and I11 spacec ra f t s and supporting s t r u c t u r e s exhibited
s a t i s f a c t o r y , i f no t excellent, i n i t i a l s o l a r absorptance and
emittance p r o p e r t i e s a s w e l l as exce l l en t s t a b i l i t y charac-
ter is t ics , A l l i nd ica t ions and observat ions i n d i c a t e t h a t a l l
S-13 su r faces w e r e i n exce l l en t condi t ion a t the t i m e of launch.
T h e major accomplis-hents r e s u i t i n g from t h e use of the S-13
p a i n t on the Pegasus s p a c e c r a f t s amounting i n each of the three
cases t o the l a r g e s t s i n g l e u s e to da t e of a thermal-control
p a i n t , included (1) the s a t i s f a c t o r y sacle-up f r o m small-size
labora tory t o 5-gal production q u a n t i t i e s of a highly spec ia l -
- -3 I 7 ILCU ~ i l e ~ I ~ , ~ ~ - ~ . ~ ; ; t r ~ l c ~ z t i ~ g , ( 2 ) cc\m.n1 r----- n + n I : r s a t i sfartnry
f i e l d app l i ca t ion of a thermal-control p a l n t t o except iona l ly
l a r g e sur face a reas , and (3) t h e successful implementation of
on-pad cleaning procedures of t h e e n t i r e upper-stage configura-
t i o n of SA-8, SA-9, and SA-10,
*
* 2 The I U , S - I V , and SMA s t ages possessed approximately 2500 f t of S-13 painted sur faces , requir ing about 20 g a l of S-13,
I l f R E S E A R C H I N S T I T U T E
20 IITRI-U6018-1
APPENDIX I
S-13 PAINT SPECIFICATION
Modification I1
Materia 1 s P a r t s by Weiqht
New Je r sey Zinc SP500 z inc oxide 240 General E lec t r ic RTV-602 s i l i c o n e 100 Toluene 170
Formulation: The z inc oxide, t he RTV-602, and 100 p a r t s
by weight of t he toluene a r e premixed and charged t o a porce la in
bal l m i l l i n a q u a n t i t y s u f f i c i e n t t o j u s t f i l l the void space
when t h e m i l l i s one-fourth f u l l of gr inding s tones 0 , 5 i n , i n
diametero The p a i n t i s ground for 3 h r a t approximately 70%
c r i t i c a l speed, The c r i t i c a l speed (rpm) i s given by:
5402 , where R i s the rad ius of t h e m i l l i n f e e t , The wc S = y = r basic charge i s then removed. and 70 p a r t s of toluene a r e added
t o t h e m i i l , . l r i e i i u i i residue 5i-i: L l i ~ ~ ~ l ~ a i i t GLG ~ T G Y G ~ : ~ t L l -. 1 -
the conten ts are uniformly t h i n , b u t not f o r more than 5 m i n ,
The conten ts are then added t o the main charge, and the whole
charge is ~,,ixed thoroughly, NOTE! THE SRC-05 CATALYST I S NOT
ADDED UNTIL THE PAINT IS APPLIED,
Prepara t ion of P a i n t f o r A p p l i c a t i o n : , The p a i n t i s fur -
nished without t h e SRC-05 c a t a l y s t , The c a t a l y s t i s added a s
1 p a r t SRC-05 i n 20 p a r t s of toluene per 670 p a r t s of S-13 (as
formulated) . This concentration r ep resen t s 0,76% c a t a l y s t
based on polymer s o l i d s , A lower concentrat ion i s recommended
i n o r d e r t o ensure optimum s t a b i l i t y t o u l t r a v i o l e t i r r a d i a t i o n
i n vacuum, A concentrat ion of 0 ,4% based upon RTV-602 provides
I I T R E S E A R C H I N S T I T U T E
21 I I T R I - U6 0 18- 1
optimum s t a b i l i t y without g rea t ly s a c r i f i c i n g terminal cure
p rope r t i e s , although a coat ing prepared a t t h i s concent ra t ion
represents the lower l i m i t without s a c r i f i c i n g cure and phys ica l
p rope r t i e s , Somewhat b e t t e r physical p rope r t i e s a r e obtained
w i t h a c a t a l y s t concentrat ion of 0,5% based on RTV-602, A
c a t a l y s t concent ra t ion of 0,4% of r e s i n s o l i d s corresponds t o
1 p a r t SRC-05 per 1 2 7 5 p a r t s of S-13; 0,5% c a t a l y s t requi res
1 p a r t c a t a l y s t per 1020 p a r t s of S-13, The c a t a l y s t should
be added a s a 2 0 : l reduct ion i n toluene, The c a t a l y s t so lu t ion
is d&&d w n i y as the paint is ----a - - A L- -,l,, LL- --,...... c UDCU aiiu LU u i i r y LIIG a l i t w u ~ ~ c . t h a t
can be appl ied i n about 30 m i n , The bulk pa in t was furnished
i n 5-gal epoxy-lined metal p a i l s , The pa in t should be thoroughly
s t i r r e d before t r a n s f e r t o o ther conta iners o r before addi t ion
of c a t a l y s t , Allow the c a t a l y s t p a i n t t o s e t f o r 10 min before
app l i ca t ion t o the primed surfaces ,
Prepara t ion of S G a c e s f o r Paint inq: Standard surface
c leaning procedures should be used t o prepare the surface f o r
app l i ca t ion of the S-13 pa in t , S-13 pa in t can, i n genera l , be
appl ied t o any surface t o which the required primer can be
appl ied , The primer, General E l e c t r i c ' s p rop r i e t a ry SS-4044,
can be appl ied t o e i t h e r anodized o r z inc chromate-primed
su r faces , It i s preferab le t h a t i t be appl ied t o c lean bare
metal o r t o anodized surf aces , however Greasy su r f aces should
be cleaned with s tandard de te rgent and water p r i o r t o priming:
they should be thoroughly dry,
I l l ' R E S E A R C H I N S T I T U T E
22 I I TRI- U 6 0 18- 1
I
Application of Paint: T h e primer can be spray-applied
(Binks model 18 o r comparable gun) a t about 30 psi , Only about
0,5 m i l of primer i s required ( j u s t enough t o provide a base f o r
the S-13 p a i n t ) . The primer should be allowed t o a i r -dry f o r
1 hr before app l i ca t ion of t h e S-13 p a i n t ,
The S-13 p a i n t can be spray-applied w i t h a Binks model 18
spray gun ( o r comparable gun) a t a gas pressure of about 60 psi,
Unless missile-grade a i r i s ava i l ab le , p repur i f i ed ni t rogen o r
p repur i f i ed a i r must be used, The S-13 p a i n t should be allowed
to a i r -cure 16 'nr, 11 13 u v i r c I M I A v f i L U ~ L ~ Y w u l n L Y u uyyL\Lu BE
KEPT O F F THE SURFACE DURING THE CURING PROCESS,
I- T- s r , r r n h n r n ~ ~ r m muhm n T ~ c r n h n m nv;ID~rc
The w e t f i l m thickness of t he p a i n t can be measured by
either the Pfund o r the Interchemical w e t - f i l m thickness gage,
or a s u i t a b l e bridge-type gage, Dry f i l m th ickness can be
measured w i t h a Fischer Permascope nondestructive thickness
tes ter , type ECTH,
Reapplication: Soi led o r damaged a reas can be recoated,
Soi led a r e a s must be cleaned thoroughly w i t h de te rgent and
water and d r i e d before appl ica t ion of add i t iona l S-13 p a i n t ,
Damaged o r gouged a reas can be recoated by making a pas t e of
S-13 i n which the bulk of the solvent i s omitted, Such a
material can be t rowelled or brushed over the damaged a reas and
cu res can be tack-free w i t h i n a f e w hours,
Storaqe of the Paint : T h e p a i n t i s suppl ied i n 5-gal
q u a n t i t i e s , Since the p a i n t cannot be mixed w i t h c a t a l y s t solu-
t i o n s i n 5-gal l o t s because of the pot l i f e of the catalyzed
I I T R E S E A R C H I N S T I T U T E
23 IITRI-U6018-1
p a i n t , i t may be d e s i r a b l e t o s t o r e t h e p a i n t i n small con ta ine r s
i n order t o avoid contamination when t h e 5-gal container i s
opened and closed a number of times. I f smaller conta iners are
u t i l i z e d , only g l a s s , n i cke l , or unlined unleaded unsoldered
s teel cans can be used, The caps, tops , o r c losu res of these
conta iners should not possess gummed s e a l s o r any mater ia l
so luble i n toluene,
Physical Proper t ies : Pa in t S-13 i s rubbery and r e s i l i e n t .
Therefore, it can be gouged by a sharp t o o l with l i t t l e e f f o r t .
I t s adherence i s exce l l en t when a primer i s used b u t i s very
poor when appl ied d i r e c t l y t o a metal s u b s t r a t e , i n which case
it can be s t r ipped f r o m t h e subs t r a t e i n one piece.
t h e r e s i l i e n c y of t h e sur face , d i r t tends t o c l i n g t o the sur-
face , D i r t can be e a s i l y removed by wiping with a w a t e r -
moistened CLEAN, SOFT cloth, NOTE: S-13 SHOULD NEVER BE
CLEANED W I T H ORGANIC SOLVENT. Paint S-13 withstands more than
10 thermal-shock cyc le s cons is t ing of immersion i n l i q u i d n i t ro -
gen followed by rapid hea t ing t o 20O0F.
t o r s i o n a l l y s t r e s s e d t o 90° without f a i l u r e and withstands re-
peated bending t o 18OoO
Because of
The p a i n t can be
O p t i c a l P roper t ies : Minimal s o l a r absorptance i s not
ob ta ined u n t i l a thickness of near ly 10 m i l s i s reached.
fol lowing t abu la t ion i s provided a s a guide,
The
I l t R E S E A R C H I N S T I T U T E
24 I I T R I -U6018-1
Thickness So la r Absorptance (50-25 m i l ) ( f i 0 , O l )
1 2 3 4 5 6 8 9 10
0,30 ,25 -23 0 2 1 0 20 0 19 .18 .17
0,17
A working range of 5 t o 8 m i l s i s recommended, For coa t ings of
5 m i l s o r t h i c k e r , t h e t o t a l hemispherical emit tance i s 0.85
o r better a t 300°K,
S t a b i l i t v t o U l t r a v i o l e t I r r a d i a t i o n i n Vacuum: The
s e v e r e s t t es t t o which t h i s mater ia l has been subjec ted was
t h a t of 7000 ESH; t h e s o l a r absorptance inc reased from 0.20 t o
0,23, wi th a Aa = 0.03.
and w a t e r before i r r a d i a t i o n does not a f f e c t s t a b i l i t y .
Cleaning wi th w a t e r o r wi th de t e rgen t
CLEAN-
ING WITH ACETONE AND OTHER ORGANIC SOLVENTS, HOWEVER, SEVERELY
AFFECTS STABILITY, Therefore , c leaning only wi th w a t e r o r with
w a t e r and de te rgen t i s requi red . Un t i l another de t e rgen t o r
wet t ing agent t h a t does no t a f f e c t s t a b i l i t y i s found, t h e use
of a 10% s o l u t i o n of Alconox (Alconox Inc . ) followed by r i n s i n g
wi th copious q u a n t i t i e s o f demineralized o r d i s t i l l e d water i s
recommended,
I I T R E S E A R C H I N S T I T U T E
25 I I T R I -U6018-1
b
L
APPENDIX I1
MEASUREMENT O F THERMOPHYSICAL PROPERTIES
Determination of Solar Absorptance: Solar absorptance i s
determined i n d i r e c t l y by measurement of s p e c t r a l r e f l ec t ance i n
the wavelength range 0 0 2 1 t o 2,7 p o The r e f l e c t a n c e d a t a a r e
in t eg ra t ed w i t h s o l a r s p e c t r a l energy d a t a for the upper atmo-
sphere ( r e f 11) t o y i e l d normalized s o l a r r e f l ec t ance . Sub-
t r a c t i o n of the s o l a r re f lec tance from un i ty y i e l d s s o l a r
absorptance, Comparison of these s o l a r s p e c t r a l energy d a t a
with the da t a of Nicolet ( ref , 1 2 ) and Johnson ( re f , 13) s h o w s
t h a t s o l a r absorptance agrees within 0,005, An IBM 7090
For t ran computer program performs t h i s i n t e g r a t i o n according t o
the mathematical d e f i n i t i o n given b e l o w :
J ws,h dl 0.2p
w h e r e W i s the s o l a r r ad ia t ion i n t e n s i t y i n the wavelength
i n t e r v a l between X and
s p e c t r a l absorptance obtained by sub t r ac t ing the s p e c t r a l re-
S , A + dh$ T h e value (1 - R X ) h i s the
f l e c t a n c e from uni ty .
Spec t r a l Solar Reflectance Measurements: Two systems w e r e
used dur ing t h i s program., One of these i s the Carymodel 1 4 ,
w h i c h i s used f o r s p e c t r a l r e f l ec t ance measurements i n the
0 2 5 - t o 2.0-p region, The Cary model 1 4 i s equipped w i t h a
I l t R E S E A R C H I N S T I T U T E
26 I I T R I -U60 18- 1
I
model 1 4 1 1 i n t e g r a t i n g sphere accessory and a recording device,
The ref lectometer i s normally used i n Type I1 operation: t h a t
i s , the sample i s i l luminated w i t h d i f f u s e , nondispersed l i g h t
and i s viewed through a small s o l i d angle a t near normal direc-
t i o n , The Cary 1 4 was used on Pro jec t C6025 (Contract No.
NAS8-11133), which involved the f i r s t s ix d e l i v e r i e s of S-13
p a i n t ,
The second u n i t i s a Beckman DK-2A instrument equipped
w i t h the standard Beckman integrat ing-=sphere attachment, I t i s
used i n Type 1 operat ion; t h a t i s , the specimen i s i l lumina ted
w i t h d ispersed l i g h t a t near-normal incidence and i s viewed
hemispherically, I t i s used i n the 0.21-to 2 , 7 - ~ region. The
DK-2A spec t roref lec tometer was used on P ro jec t U6018 (Contract
No, NAS8-11967), w h i c h involved d e l i v e r i e s 7 through 11.
E x i t t a ~ z e Measurements: Ar! evacl~atec? c a l n r i m e t r i c device
was used for measuring the t o t a l hemispherical emittance of the
S-13 specimens i n the -40 t o +40°F range, This instrument
\ i t i l i z s s LLI.r- CIIC CYUIIAULIUl l l ----: 1 4 k - 4 > r m tnnhni buu.--&-y-- m i l e fnr --- d p t p r m i n a t i o n -- ---- of emittance.
The sample i s deposi ted on a 1- in . cube, which contains a
r e s i s t a n c e h e a t e r , Thin p o w e r leads support the cube i n s i d e a
l i q u i d nitrogen-cooled sphere, which i s coated w i t h a black
p a i n t , The sphere i s , i n t u rn , contained i n a vacuum system to
e l imina te convection losses, Nonradiative l o s s e s from the cube
are taken i n t o account,
' I I
,
i i i I
1 1 I
! i
APPENDIX I11
SPACE (SOLAR) SIMULATION CHAMBERS
The workhorse, t h e ion-pumped space s imula t ion chamber,
i s shown i n Figure 2 . The chamber i s provided wi th a q u a r t z
window and a l iquid-cooled t a b l e , The t a b l e can be cooled wi th
l i q u i d n i t rogen , i ce water , o r t a p water (or hea ted f l u i d s ) and
can accommodate twelve 1 x 0.5-in, specimens, The system con-
sists of a 400-l i ter /sec Varian VacIon pump and a mechanical
forepump. An AH-6 lamp i s mounted over t h e q u a r t z window.
Dmmvfi,4,,mi kle e-..< ..,-l --L ---I J=- - I *.ur.L V U U b A U y u A v a I c i i L DULQL L ~ U L O L S , ds determined wi tn a
temperature-compensated thermopile, can be achieved f r o m 1 t o
15 s o l a r i n t e n s i t i e s i n t h e 2000- t o 4000-A wavelength region. 0
I n a d d i t i o n t o t h e workhorse chamber described above, a
multiple-chamber ion-pumped system, c a l l e d the Quad-Ion system,
was used f o r s t u d i e s i n which d i f f e r e n t exposures? d i f f e r e n t
i n t e n s i t i e s , and d i f f e r e n t temperatures a r e r equ i r ed w i t h the
s a m e se t of AH-6 lamps. T h i s system has been p a r t i c u l a r l y use-
f u l i n s tudying r e c i p r o c i t y e f f e c t s and f i l t e r e f f e c t s on
engineer ing coa t ings . A photograph of t h e system i s given i n
Figure 3 .
i l l R E S E A R C H I N S T I T U T E
28 I I T R I - U6 0 1 8- 1
Figure 2
VACION SOLAR SIMULATION CHAMBER
29 I ITRI 46018-1
i
30 IITRI-U6018-1
I '
REFERENCES
1,
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4 ,
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13
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Z e r l a u t , G , A , , G i l l i g a n , J, E . , and H a r a d a , Yo, "Stable W h i t e C o a t i n g s , i i I I T R e s e a r c h I n s t i t u t e R e p o r t No, I I T R I - C 6 0 2 7 - 1 6 ( I n t e r i m Technical Progress R e p o r t ) , JPL C o n t r a c t N o , 950746.
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C o n t r a c t No , N A S 8 - 1 1 1 3 3 , G e o r g e C. Marshall Space F l i g h t C e n t e r ( the o r i g i n a l contract r e l a t i n g t o this r e p o r t j .
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Zoller, L o K O , "S-13 T h e r m a l C o n t r o l C o a t i n g fo r SA-9/ Pegasus A Spacecraft," I n t e r n a l N o t e IN-P&VE-M-65-4, G e o r g e C , Marshall Space F l i g h t C e n t e r , June 22 , 1965.
B a d i n , F, E,; " F i n a l R e p o r t - R a d i a t i v e Property Measure- ments a t KSC, ( I F a i r c h i l d - H i l l e r C o r p o r a t i o n Memo R e f e r e n c e EMTL-142, March 1, 1.965,
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N i c o l e t , M , , C h a p t e r X I 1 i n "Solar Physics and the A t m o - sphere of the E a r t h , " C. S. W h i t e and 0. 0. B e n s o n , Jr., ed., Univ, of New Mexico Press, A l b u q u e r q u e , 1952.
I l l R E S E A R C H I N S T I T U T E I
I I I T R I - U 6 0 1 8 - 1 31
I ~
